Triumphrat

sonofrust · 12-31-2008, 12:19 AM

Went in to the local BMW/Triumph dealership last week to buy an oil filter for my BMW and fell in love with a cherry '06 Thruxton with about 4500 miles. This bike is FUN! I'm 6' 2" and weigh in at about 270. Wife says the bike looks too small; I say who cares, it's a hoot to ride and looks great in my garage. A bit whimpy me thinks for a 900, especially at my mile-high altitude. Came with the TORS pipes (sounds nicer than stock) and groovy bar-end mirrors. Thinking that an air box remove and rejet is in my future. Did a bit of research on this site re. rejetting. Of course, the data I found does not take altitude into account. Is there a rule of thumb in terms of jet size reduction as altitude increases? Someone said cut recommended jet size by 5% for my 5300 ft. rise above sea level. Any advice?

Thanks!

Doug

triton_750 · 12-31-2008, 02:02 AM

Quote:

Originally Posted by sonofrust

Went in to the local BMW/Triumph dealership last week to buy an oil filter for my BMW and fell in love with a cherry '06 Thruxton with about 4500 miles. This bike is FUN! I'm 6' 2" and weigh in at about 270. Wife says the bike looks too small; I say who cares, it's a hoot to ride and looks great in my garage. A bit whimpy me thinks for a 900, especially at my mile-high altitude. Came with the TORS pipes (sounds nicer than stock) and groovy bar-end mirrors. Thinking that an air box remove and rejet is in my future. Did a bit of research on this site re. rejetting. Of course, the data I found does not take altitude into account. Is there a rule of thumb in terms of jet size reduction as altitude increases? Someone said cut recommended jet size by 5% for my 5300 ft. rise above sea level. Any advice?

Thanks!

Doug

Hey Doug - Congrats on the new purchase! I think the Thruxton does appear a little small but only when compared to some big fat HD!

Anyway to answer your question - for more power definitely remove the airbox, it's way too restrictive if you have more free-flowing pipes. According to the Jenks Bolts "tuning notes for the Bonneville family" (incl. Thruxton), the very last para says to reduce main jets by 5% between 3000' & 6000' and for every further 1000' reduce it again by about 3%. You should be able to download it from the internet - it's well worth the read if you're going to do this yourself. I did it a couple of months back using the jets that British Customs supplied and everything worked out well - the bike is so much better with the K&N's, rejetted and Predators, although way louder than before!
Best of luck & welcome to forum!
Cheers
Steve